The present invention pertains to communication systems and more particularly to server availability for pooled server architectures.
In modern communication systems, clients typically receive periodic advertisement from servers of a common pool indicating their availability and current traffic loading. The advertisement includes the status of each of a number of pooled servers. The client then typically performs a probabilistic selection from the pool based on the server's capacity. For example, if three servers had a capacity of 10, 40 and 50 call units, they would be selected approximately 10%, 40% and 50% of the time respectively.
If one of the servers from the pool is unavailable due to either network or server difficulties, the selection percentages remaining in effect until the network or server fault can be detected. If the frequency of a server's, or any other resource's, selection is significantly higher than the frequency with which the fault is detected, the faulty server or resource may be selected for use many times during the time period until the fault is detected.
During the faulty server time period, all attempted selections of the faulty server will lead to an increase in call setup time. Further, continued selection failures could result in loss of the call by the communication system. Such loss of the call may affect revenue by the communication system operator and sub-standard call services, as measured by a public utility commission, being supplied to a number of communication system users.
Further, unnecessary retries of server selection during a fault condition cause an increase in network and server central processing unit (CPU) utilization without calls being successfully connected. Such situation could exacerbate a transient server fault and network congestion.
Accordingly, it would be highly desirable to have a server lottery selection method which provides a low cost method for a client to dynamically adjust the probability of server selection during faulty conditions.